1. Field of the Invention
The present invention relates to motion dampening devices and more specifically to a bidirectional hydraulic damper of the reciprocating piston type with spring centering and a spring loaded hydraulic reservoir.
2. Prior Art
Hydraulic dampening devices well known in the art employ a cylinder and a piston rod reciprocating in the cylinder. A piston on the end of the rod sealingly engages the cylinder wall and divides the cylinder into two asymmetrical hydraulic chambers. Restrictive passages between the two chambers retard the rate of fluid flow therebetween to provide a damping action. To compensate for loss of fluid from leakage and thermal volume changes, a fluid reservoir may be provided as exemplified by U.S. Pat. Nos. 3,933,337 issued Jan. 20, 1976 to Morris et al.; 3,944,031 issued Mar. 16, 1976 to Cholet et al and 4,099,602 issued Jul. 11, 1978 to Kourbetsus. generally employ valve mechanisms in the passages and provide asymmetrical damping forces. These are trouble prone, expensive to manufacture and maintain, and provide no convenient means for checking and refilling the fluid reservoir. Their structure is so complex that they are not adaptable to size reduction for those applications requiring light weight and small size such as flight control surfaces.